A very tricky question indeed.
First of all...I have been flying over 6 years for one of the fastest growing airlines in the world...Yep...it IS based in the Middle East! I have had the opportunity to fly with all the latest types of heavy metal.
But without wanting to go in to a polemic regarding Middle Eastern Airlines, be aware that you will come here to work really hard (1000hrs/year) and that you will be looked upon as a slave.
While living and working in the Middle East used to be able to provide you with a certain lifestyle, these days many of that has dissappeared due to erroding T&Cs, dwindling exchange rates and huge pilot shortages.
So dont come here for the lifestyle, only come here for a certain career progression. Upgrades will be offered to you maybe or maybe not. Depending on the company you will choose...But it might easily take you 4 years from date of joining, a term which has proven itself to be too long for many others.
On the other hand, I think the old adagio of "never leave an upgrade or a typerating untouched" does not have that much value anymore than it used to have. Aviation is changing and for sure opportunities will be around for some years to come.
I am faced with the same question as you are facing. After 6 years here I am finally offered an upgrade. But both my wife and I are fed up with the place and its lifestyle. At the same time I am offered a job back home. Less money and less apealing airplanes, but with some sort of a normal lifestyle which allows me to be closer to family and real friends (exactly, the M.E. will bring you many people to know, but very very few real friends to have).
So 90% it is decided, I will leave the M.E and a possible upgrade behind in lieu of a better lifestyle....
All I want to say is....do what you think is right. Do not listen too much to others but follow your gut feeling. Dont get stuck following old sayings etc...
But remember....The grass is only greener on the other side as a result of the
underneath it!